Abstract
The non-Typhi Salmonella (NTS) infection is critical to children’s health, and the ceftriaxone is the important empirical treatment choice. With the increase resistance rate of ceftriaxone in Salmonella, the molecular epidemiology and resistance mechanism of ceftriaxone-resistant Salmonella needs to be studied. From July 2019 to July 2020, a total of 205 NTS isolates were collected, 195 of which (95.1%) were cultured from stool, but 10 isolates were isolated from an extraintestinal site. Serogroup B accounted for the vast majority (137/205) among the isolates. Fifty-three isolates were resistant to ceftriaxone, and 50 were isolated from children younger than 4years of age. The resistance rates for ceftriaxone, ciprofloxacin, and levofloxacin were significantly higher in younger children than the older children. The resistance genes in the ceftriaxone-susceptible isolates were detected by PCR, and ceftriaxone-resistant Salmonella were selected for further whole-genome sequencing. Whole-genome analysis showed that serotype Typhimurium and its monophasic variant was the most prevalent in ceftriaxone-resistant isolates (37/53), which comprised ST34 (33/53), ST19 (2/53), and ST99 (2/53), and they were close related in the phylogenetic tree. However, the other isolates were diverse, which included one Enteritidis (ST11), one Indiana (ST17), one Derby (ST40), four Kentucky (ST198), two Goldcoast (ST2529, ST358), one Muenster (ST321), one Virchow (ST359), one Rissen (ST469), one Kedougou (ST1543), two Uganda (ST684), and one Kottbus (ST8839). Moreover, CTX-M-55 ESBLs production (33/53) was found to be mainly responsible for ceftriaxone resistance, followed by blaCTX-M-65 (12/53), blaCTX-M-14 (4/53), blaCTX-M-9 (2/53), blaCTX-M-64 (1/53), blaCTX-M-130 (1/53), and blaCMY-2 (1/53). ISEcp1, IS903B, IS Kpn26, IS1F, and IS26 were connected to antimicrobial resistance genes transfer. In conclusion, the dissemination of ESBL-producing Salmonella isolates resulted in an increased prevalence of ceftriaxone resistance in young children. The high rate of multidrug resistance should be given additional attention.
Highlights
Salmonella is a genus of Gram-negative bacteria of the family Enterobacteriaceae, and Salmonella enterica subsp. enterica is the most frequent pathogen triggering human sickness (Smith et al, 2016)
The isolates from feces accounted for the vast majority (195/205), and the remaining 10 isolates were from several types of sterile body fluids
Previous research indicated that non-Typhi Salmonella (NTS) isolates from children aged 5 years, with a similar elevated resistance rate to cephalosporins and quinolones (Liang et al, 2015), which is consistent with our results
Summary
Salmonella is a genus of Gram-negative bacteria of the family Enterobacteriaceae, and Salmonella enterica subsp. enterica is the most frequent pathogen triggering human sickness (Smith et al, 2016). Salmonella is a genus of Gram-negative bacteria of the family Enterobacteriaceae, and Salmonella enterica subsp. Salmonella infection is officially called as salmonellosis, which causes stomach cramps, diarrhea, and fever. Salmonellosis is a global health issue, with approximately 93 million cases of gastroenteritis and 155,000 associated deaths caused by Salmonella every year worldwide (Majowicz et al, 2010). In contrast to Salmonella Typhi and Salmonella Paratyphi that are rarely encountered outside endemic countries or in returning travelers, NTS has a high worldwide distribution. NTS infections are usually self-limiting, and antibiotics are not indicated for uncomplicated infections. Antibiotic therapy needs to be considered for populations at increased risk for invasive infections, such as neonates and elderly person, and antimicrobial treatment should be modified or discontinued when a clinically plausible organism is identified (Shane et al, 2017)
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